Outer surface of a grill



FIG. 1 is an elevated right front perspective view of the outer surface of a grill, showing our new design;

FIG. 2 is a front view of our new design;

FIG. 3 is a right side view thereof; and,

FIG. 4 is is left side view thereof. 

The ornamental design for an outer surface of a grill, as shown and described. 